Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
2002-04-17
2004-05-11
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S213000, C428S323000, C428S336000, C428S337000, C428S339000, C428S480000, C428S483000, C428S910000, C528S275000, C528S277000, C528S279000, C528S283000, C528S285000, C528S293000, C528S295000
Reexamination Certificate
active
06733873
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polyester film for dry film resists. More specifically, it relates to a polyester film for dry film resists, which is excellent in terms of transparency, slipperiness, winding properties, separation work efficiency and resolution.
PRIOR ART
In recent years, a dry film resist (may be abbreviated as DFR hereinafter) method has been used to produce a printed wiring circuit board. A photoresist laminate used in this DFR method is generally a laminate structure comprising a base layer, a photoresist layer and a protective layer laminated in the mentioned order and a polyester film having excellent mechanical, chemical and optical properties has been used as the base layer.
The DFR method comprises removing the protective layer of the photoresist laminate having the above structure, joining the exposed photoresist layer to a conductive matrix mounted on a substrate and joining a glass sheet printed with an electronic circuit to the photoresist film base layer. Thereafter, the resulting laminate was exposed to ultraviolet radiation having a wavelength around 365 nm from the glass sheet side to exposure and cure a photosensitive resin constituting the photoresist layer, the glass sheet and the base layer are removed, and an uncured portion of the photoresist layer is removed by a solvent or the like. Further, when etching is carried out with an acid, the exposed conductive matrix dissolves, the photoresist resin reacts, and an unremoved portion of the conductive matrix remains as it is. When the remaining photoresist layer is then removed by suitable means, the conductive matrix layer is formed on the substrate as a circuit.
A polyester film used as the base layer in the above DFR method is required to have high transmission of light having a wavelength around 365 nm and a low haze value. When the photoresist layer is to be exposed, as light passes through the base layer, if the transmission of the base layer is low, the photoresist layer may not be exposed fully or light may be scattered with the result of poor resolution.
In recent years, portable telephones, PHS and personal computers have been in growing demand and the improvement of productivity of photoresist films for the production of electronic circuits for use in these devices has been required.
To improve handling ease for the production of photoresist films or the handling ease of a photoresist film, the polyester film of the base layer is required to have moderate slipperiness, winding properties and tear strength. The method of forming fine protrusions on the surface of a polyester film by containing fine particles in the film has been used to achieve the above properties. JP-A 7-333853 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) proposes a biaxially oriented laminated polyester film for photoresists in which the outermost layer on at least one side contains particles (globular or amorphous silica particles, globular crosslinked polymer particles, etc.) having an average particle diameter of 0.01 to 3.0 &mgr;m and has a surface roughness Ra (center line average roughness) of 0.005 &mgr;m or more, an Rt (maximum height) of less than 1.5 &mgr;m and a film haze of 1.5% or less.
However, this polyester film may be unsatisfactory in terms of transmission of light having a wavelength around 365 nm with the result of reduced resolution, thereby making it difficult to obtain a fine circuit pattern. Further, the above laminated polyester film has a problem such as high production cost.
As the recent enactment of a home electric appliance recycling law promotes the recycling of electric products and products for producing the same, materials constituting these are required to contain no antimony, tin or lead. Antimony compounds have been used as a polycondensation catalyst for producing a polyester polymer for forming a polyester film. Use of polycondensation catalysts other than these antimony compounds is now desired.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polyester film for dry film resists, which solves the above problems of the prior art and meets requirements for the transmission of light, especially light having a wavelength around 365 nm, slipperiness, winding properties and resolution.
It is another object of the present invention to provide a polyester film for dry film resists, which further has excellent recyclability in addition to the above properties.
It is still another object of the present invention to provide a laminated polyester film for dry film resists, which prevents reflection and has excellent fine pattern circuit formability in addition to the above properties.
It is a further object of the present invention to provide a dry film resist comprising the above polyester film of the present invention as a base film.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a biaxially oriented polyester film for dry film resists, which comprises (1) an aromatic polyester containing metals derived from a polycondensation catalyst in a total amount of less than 150 ppm and metal antimony out of the above metals in an amount of 15 mmol % or less based on the total of all the acid components and which has (2) a haze value of 3% or less, (3) a transmission of ultraviolet radiation having a wavelength of 365 nm of 86% or more and (4) a thickness of 10 to 25 &mgr;m.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by a laminated polyester film which comprises (1) the above biaxially oriented polyester film of the present invention and a lubricating layer formed on at least one side of the polyester film and which has (2) a haze value of 3% or less and (3) a transmittance of ultraviolet radiation having a wavelength of 365 nm of 86% or more.
According to the present invention, thirdly, the above objects and advantages of the present invention are attained by a dry film resist comprising the biaxially oriented polyester film or laminated polyester film of the present invention, a photoresist layer and a protective film layer laminated in the mentioned order.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described in detail hereinbelow. A description is first given of the biaxially oriented polyester film of the present invention.
The aromatic polyester constituting the film of the present invention is preferably a polyethylene terephthalate homopolymer or a copolymer comprising ethylene terephthalate as the main recurring unit. The polyethylene terephthalate homopolymer is suitably used in a DFR film because it has high mechanical strength and a high transmission of short-wavelength visible radiation and near ultraviolet radiation close to that radiation.
In the present invention, the comonomer of the copolyester may be a dicarboxylic acid component or diol component. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as isophthalic acid and phthalic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Examples of the diol component include aliphatic diols such as 1,4-butanediol, 1,6-hexanediol and diethylene glycol; alicyclic diols such as 1,4-cyclohexanedimethanol; and aromatic diols such as bisphenol A. They may be used alone or in combination of two or more. Out of these, isophthalic acid is particularly preferred because it gives a copolymer having high transparency and tear strength.
The amount of the comonomer which depends on its type is such that the melting point of the obtained polymer should be 245 to 258° C. (melting point of the homopolymer). When the melting point is lower than 245° C., heat resistance deteriorates, heat shrinkage
Kubo Koji
Mizutani Kei
Chen Vivian
Teijin Limited
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